William Hayes Fisher, 1st Baron Downham, PC, KStJ (1853 – 2 July 1920) was a British Conservative Party politician.

He was educated at Haileybury and University College, Oxford, and was called to the Bar, Inner Temple, in 1879.

In 1896 he was appointed a Junior Lord of the Treasury (government whip) in the Conservative administration of Lord Salisbury, a post he held until August 1902, and then served under Arthur Balfour as Financial Secretary to the Treasury from 11 August 1902 to April 1903, when he resigned as a result of his connection with a financial syndicate.

He retained this post also when David Lloyd George became Prime Minister in December 1916, but in June 1917 he was promoted to President of the Local Government Board with a seat in the cabinet.

Apart from his career in national politics, Fisher was an Alderman of the London County Council between 1907 and 1913 and its Chairman in 1919.